Hi David, Am Mittwoch, 12. Juli 2017, 16:38:09 CEST schrieb David.Wu: > Hi Doug, > > 在 2017/7/12 1:03, Doug Anderson 写道: > > Hi, > > > > On Fri, Jul 7, 2017 at 9:03 PM, David Wu <david.wu@xxxxxxxxxxxxxx> wrote: > >> @@ -6,7 +6,13 @@ Required properties: > >> "rockchip,rk3288-pwm": found on RK3288 SoC > >> "rockchip,vop-pwm": found integrated in VOP on RK3288 SoC > >> > >> - reg: physical base address and length of the controller's registers > >> > >> - - clocks: phandle and clock specifier of the PWM reference clock > >> + - clocks: See ../clock/clock-bindings.txt > >> + - For older hardware (rk2928, rk3066, rk3188, rk3228, rk3288, > >> rk3399): > >> + - There is one clock that's used both to derive the functional > >> clock > >> + for the device and as the bus clock. > >> + - For newer hardware (rk3328 and future socs): specified by name > >> + - "pwm": This is used to derive the functional clock. > >> + - "pclk": This is the APB bus clock. > > > > I'm pretty sure that that the above description doesn't quite match the > > code. > > > > * The above description says that for old hardware there is one clock > > and 'clock-names' was not necessary (though as I understand it it's OK > > if it's there). > > > > * The old code matched the old description. AKA: if there was no > > "clock-names" then everything was OK. > > > > * The new code will not work if there was no "clock-names". > > > > Many of the old devices had a clock-names present (and it was "pwm"), > > but not all. Specifically it looks like > > "arch/arm/boot/dts/rk3xxx.dtsi" doesn't specify a clock-names. > > So we can keep code: the pc->clk = devm_clk_get(&pdev->dev, NULL); > If the name is NULL, we can get the first clk defined at DTB. I don't think it will work that way. clk_get with NULL argument will likely grab the first clock of the list independent of clock-names being present. It might be better to do something like [pseudo-code]: pwm->pclk = clk_get( ..., "pclk"); if (IS_ERR(pwm->pclk)) pwm->pclk = NULL; pwm->pwm_clk = clk_get(..., "pwm"); if (IS_ERR(pwm->pwm_clk)) pwm->pwm_clk = clk_get(..., NULL); if (IS_ERR(pwm->pwm_clk)) return PTR_ERR(pwm->pwm_clk); That way, you make your way backwards through the pwm-binding-history. Ending at the single-clock without clock-names property as the last fallback. Heiko -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
